1. The University of Adelaide, School of Computer Science
30 December 2018
Computer Networks, 5th Edition
Chapter 6
Congestion Control and Resource Allocation
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Chapter 2 — Instructions: Language of the Computer

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FIGURE 6.1 A potential bottleneck router.
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FIGURE 6.2 Multiple flows passing through a set of routers.
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FIGURE 6.3 Ratio of throughput to delay as a function of load.
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FIGURE 6.4 One four-hop flow competing with three one-hop flows.
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FIGURE 6.5 (a) FIFO queuing; (b) tail drop at a FIFO queue.
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FIGURE 6.6 Round-robin service of four flows at a router.
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FIGURE 6.7 Example of fair queuing in action: (a) Packets with earlier finishing times are sent first; (b) sending of a packet already in progress is completed.
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FIGURE 6.8 Packets in transit during additive increase, with one packet being added each RTT.
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FIGURE 6.9 Typical TCP sawtooth pattern.
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FIGURE 6.10 Packets in transit during slow start.
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FIGURE 6.11 Behavior of TCP congestion control. Colored line = value of CongestionWindow over time; solid bullets at top of graph = timeouts; hash marks at top of graph = time when each packet is transmitted; vertical bars = time when a packet that was eventually retransmitted was first transmitted.
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FIGURE 6.12 Fast retransmit based on duplicate ACKs.
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FIGURE 6.13 Trace of TCP with fast retransmit. Colored line = CongestionWindow; solid bullet = timeout; hash marks = time when each packet is transmitted; vertical bars = time when a packet that was eventually retransmitted was first transmitted.
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FIGURE 6.14 Computing average queue length at a router.
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FIGURE 6.15 Weighted running average queue length.
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FIGURE 6.16 RED thresholds on a FIFO queue.
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FIGURE 6.17 Drop probability function for RED.
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FIGURE 6.18 Congestion window versus observed throughput rate (the three graphs are synchronized). Top, congestion window; middle, observed throughput; bottom, buffer space taken up at the router. Colored line = CongestionWindow; solid bullet = timeout; hash marks = time when each packet is transmitted; vertical bars = time when a packet that was eventually retransmitted was first transmitted.
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FIGURE 6.19 Trace of TCP Vegas congestion-avoidance mechanism. Top, congestion window; bottom, expected (colored line) and actual (black line) throughput. The shaded area is the region between the α and β thresholds.
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FIGURE 6.20 An audio application.
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FIGURE 6.21 A playback buffer.
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FIGURE 6.22 Example distribution of delays for an Internet connection.
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FIGURE 6.23 Taxonomy of applications.
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FIGURE 6.24 Two flows with equal average rates but different token bucket descriptions.
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FIGURE 6.25 Making reservations on a multicast tree.
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FIGURE 6.26 RED with In and Out drop probabilities.
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FIGURE 6.27 Diagram for Exercise 6.
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FIGURE 6.28 TCP trace for Exercise 27.
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